1. Field of the Invention
The disclosures discussed herein relate to an image forming apparatus.
2. Description of the Related Art
There is provided a commercially available image forming apparatus having a configuration in which toner images formed on a photoconductor are transferred onto an intermediate transfer belt, the toner images formed on the intermediate transfer belt are secondarily transferred and printed onto a sheet of paper while passing through an interval between the intermediate transfer belt and a transfer roller coming into contact with the intermediate transfer belt.
In such an image forming apparatus, the difference or fluctuation may occur between the circumferential velocity of the rotating intermediate transfer belt and the sheet transporting velocity during the toner images formed on the intermediate transfer belt being secondarily transferred onto the sheet. This may result in degradation of image qualities as well as misalignment of toner images, in a case of duplex printing, on two surfaces of the sheet due to deviation of the positions at which the toner image on the intermediate transfer belt are transferred onto the sheet, deviation of the image positions, non-uniform density, and the like.
Japanese Laid-open Patent Publication No. 11-52757, for example, discloses a configuration to eliminate the above drawbacks. In the disclosed configuration, a torque limiter configured to transmit drive force at a torque less than that obtained when the transfer roller being in contact with an intermediate transfer belt is disposed in a drive mechanism between a drive unit configured to drive a transfer roller and the transfer roller. In this configuration, the transfer roller is brought into contact with the intermediate transfer belt at the velocity faster than the velocity of the intermediate transfer belt, which causes the torque limiter to slip. As a result, the intermediate transfer belt is driven to rotate with constant velocity in accordance with the traveling (rotations) of the intermediate transfer belt.
With such a configuration, since the transfer roller is driven by following the traveling (rotations) of the intermediate transfer belt, the circumferential velocity of the intermediate transfer belt and the sheet transporting velocity are maintained at a constant velocity, which prevents degradation of the image quality due to deviation in positions of the transferred images.
However, in the image forming apparatus having a contact/separate mechanism between the intermediate transfer belt and the transfer roller, the toner images on the intermediate transfer belt may be misaligned or disarrayed, due to impact applied to the intermediate transfer belt when the transfer roller and the intermediate transfer belt come into contact with each other or are separate from each other. Further, the velocity of the intermediate transfer belt fluctuates while the transfer roller is separate from the intermediate transfer belt, which may degrade the image quality due to deviation in the positions of the toner images transferred from the photoconductor. Specifically, when the transfer roller is brought into contact with the intermediate transfer belt at the velocity faster than that of the intermediate transfer belt, the impact applied from the transfer roller to the intermediate transfer belt is enormous and hence, the degradation of image quality may become significant.